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CHRIS CUOMO, CNN ANCHOR: Welcome to all our viewers in the United States, I'm Chris Cuomo, special edition of "STARTING POINT" here in Boston with John Berman.

JOHN BERMAN, CNN ANCHOR: Bostonians still very much reeling this morning from this shock of a terrorist attack in their city. Our city, it's my hometown. As we've been telling you, there's three people dead in these twin bombings at the Boston Marathon, such an iconic day in this city.

One of those killed, this young, beautiful boy. The "Boston Globe" identifies him as 8-year-old Martin Richard. He came to see his father run in the marathon, came to give him a hug at the end of the race and ends up right in the middle of the blast, his sister also there.

She lost a leg. His mother also suffered injuries in a hospital overnight. We're hearing possible brain injury, just awful. They're among the 144 people who are wounded in this attack.

CUOMO: Thoughts and prayers go out, could not imagine being that father on this morning. Everything he cares about the most, in some type of desperation now, or loss. Just one story of many, as John said, 144 or more casualties, just as many families left to deal with this.

We are following that with team coverage to let you know the latest, many still fighting for their health right now. We'll give you the latest on that two tracks because of this investigation, as well.

Overnight, authorities spent hours, we were watching them canvassing this city and this square, searching a particular apartment in Revere, Massachusetts, leaving with bags of evidence. The question is why, what they find? No words on any arrests yet.

We know that there's this location about 5 miles away. Pam Brown is on the scene there with the latest. What do we know now?

PAMELA BROWN, CNN CORRESPONDENT: Well, Chris, as you mentioned, I'm here in Revere, Massachusetts. About 15 minutes away from where the explosions went off yesterday. This morning no activity here at the amount complex behind me, but we have seen several law enforcement vehicles around the area.

Authorities searched a fifth floor apartment inside the Ocean Shore Complex for eight hours starting around 5:00 yesterday afternoon. A federal law enforcement official tells CNN's Susan Candiotti the resident of that apartment gave authorities consent to conduct that search.

Officials were seen leaving the complex with boxes. We did speak to one resident. She says that she is scared to think that a person possibly connected with yesterday's explosion may live here.

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UNIDENTIFIED FEMALE: I'm afraid because I don't know who is here, who lives here, you know.

(END VIDEO CLIP)

BROWN: Authorities tell us that at this point no arrests have been made. No one is in custody. Of course, we will keep you updated -- Chris.

BERMAN: All right, Pam Brown in Revere, our thanks to you. Of course, again, that apartment being searched overnight, we're still learning what the investigators may have taken out of that apartment.

It's just one piece of this investigation. Focus right now on this city but in Washington, also, there is so much going on. President Obama says those responsible for bombing the Boston Marathon, they will not escape justice.

Speaking last night at the White House, the president promised to find out who did it and promised to find out why. He also reached out to leaders in Congress, saying this is a time for unity among Americans.

CNN's Brianna Keilar is standing by at the White House this morning. Brianna, do we expect to hear more from the president today?

BRIANNA KEILAR, CNN WHITE HOUSE CORRESPONDENT: John, there's no official word from the White House that we will. But I will tell you that he is supposed to be at an event at 3:00 p.m. which was previously scheduled to honor the NASCAR Sprint Cup champion.

You can kind of see how that would -- that's sort of a light event and it wouldn't be far from the realm of expectation that that may be canceled. In fact, talking to sources this morning, I'm getting the sense that that's definitely in consideration.

But President Obama according to a White House official was briefed overnight. He's very much focused on what happened in Boston and moving forward trying to figure out who did this and why they did this.

He was briefed overnight by his Homeland security adviser. He's going to be briefed again this morning by his Homeland Security Adviser Alissa Monaco, as well as the FBI Director Robert Mueller.

And we'll be waiting to see if he says something else in addition to his comments yesterday where he said that the U.S. will respond. (BEGIN VIDEO CLIP)

BARACK OBAMA, PRESIDENT OF THE UNITED STATES OF AMERICA: We still do not know who did this, or why, and people shouldn't jump to conclusions before we have all the facts. But, make no mistake, we will get to the bottom of this, and we will find out who did this, we'll find out why they did this. Any response -- any responsible individuals, any responsible groups, will feel the full weight of justice.

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KEILAR: But here's what we're looking for today from the White House, John. At 1:15 p.m. Jay Carney is on the schedule to brief. Then again as I said before 3:00 p.m. Eastern, President Obama was supposed to be at that NASCAR event, which would give him an opportunity to speak to the public. But all of this is subject to change certainly and we will not be surprised if it does.

BERMAN: All right, Brianna Keilar at the White House. Thanks so much for being with us this morning. We want to bring in Tagg Romney. You may recognize Tagg. Tagg is Mitt Romney's son. He's also a Boston resident, and like all Boston residents, he knows just how important Patriot's Day is.

It is hard to explain to people not from Boston what an important day it is. Tagg was at the Red Sox game, on his way to the marathon, walking the streets, as the explosion happened. What did you see?

TAGG ROMNEY, SON OF MITT ROMNEY: You're right about Boston. Boston is about sports and culture and history and this day is a convergence of those three things. We were at Fenway watching the morning Red Sox game. We came out to watch the end of the marathon and we had just happened in a cab 2 or 3 minutes before the explosion happened and were on our way back home. It's such a horrifying and sickening event.

BERMAN: I was trying to explain to people for Bostonians. There is zero degrees of separation between anyone from Boston and people who were involved with this attack. Either know someone who was right there. You know someone who was running or you were standing on the sidelines yourself. It is a punch in the gut.

ROMNEY: It is really. This day is like Christmas for Bostonians. The Bruins are playing. The Celtics are playing, the marathon, a celebration of independence. The first shots were fired at Lexington green and it is such an important day. Our prayers are with the victims and those who are suffering. It really is a horribly tragic event.

CUOMO: Families, you know, you've got your son with you here this morning, beautiful kid. When you see that picture of that little boy, and that father, he's running a race, his family is there to embrace him and he winds up almost losing all of them.

ROMNEY: Such a cowardly act whoever did this. And then you see the warmth of the first responders, and the people around who rushed to the scene such a contrast to their bravery. And, it just really is a family event and it's the best of Boston. It's wonderful to see how people have been responding, how people are pulling together.

BERMAN: Are you and yours all OK? I know it was 45 minutes, trying to get in touch with my sister who works on the block. It was hard to find people after the event.

ROMNEY: We had family who were running in the marathon who had just crossed the finish line a few minutes earlier. It's senseless. It doesn't make any sense.

CUOMO: What can you guys say about the people and the heart that's in this city in terms of how we'll move forward from something like this?

ROMNEY: Bostonians are resilient. They're going to come together. They messed with the wrong people. There's going to be a period of grief, I'm sure there will be some anger. And we're going to want to figure out how to keep this from happening again. Not just here but all over the country.

BERMAN: One of the things I heard last night, some were saying, this is Boston's 9/11. No, no, Boston actually was part of 9/11. Two of the planes took off from here. This is a city that very much has dealt with tragedy in the past, and has responded, you know, with strength, with vigor.

It will happen again. Everyone I've seen, you know, since I stepped foot in this city last night telling us be safe. You know, be together. We're all here for each other.

ROMNEY: Yes. It's a wonderful city and families very strong here and I think this will actually end up bringing us closer together.

CUOMO: Tagg, thank you for joining us this morning.

ROMNEY: Absolutely.

CUOMO: Glad everybody's OK.

ROMNEY: Thanks.

CUOMO: You're welcome.

BERMAN: All right, so not just here but across the nation, swift reaction to these attacks. Americans pulling together everywhere in a show of unity even on Capitol Hill.

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REP. JOHN BOEHNER (R), OHIO: The House will now observe a moment of silence in memory of the victims of today's attack in Boston.

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BERMAN: The U.S. House of Representatives paused in its official business just after 5:00 yesterday. That was a little more than two hours after the bombings. You know, Major League Baseball around the country last night, moments of silence were observed before the games got under way. This was the scene in Minneapolis, where the Twin and Angels took the field.

CUOMO: You saw it repeated all over the country. Boston College, one of the big universities here, is going to post a healing mass this afternoon. The school is at mile 21 on the marathon route, about 5 miles from where the blast occurred.

Several hundred students ran the race to help raise money for the school and as we've all heard, the last mile of the race had been dedicated to the families in Newtown. They were present here. Luckily no one was hurt and now these communities have to come together once again to hold each other closer in this time of need.

BERMAN: You know, at sporting events all over the country, all over the world, are going to have to take into account, the Celtics game tonight was canceled. They're not going to play it at all since the playoffs are set.

London is set to hold a marathon coming up on Sunday and officials there say they expect the race to take place as planned, but as you can imagine, security preparations will be reviewed in the wake of the attacks here. Tens of thousands of competitors and spectators are expected to turn out.

CUOMO: Obviously these Boston bombings, you know, dominant in terms of the world story that we're dealing with since the event draws people from literally 100 countries. So we have the newspapers here and around the world, you know, we're going to see reactions all day.

We're start showing you pictures of the papers. We have "The Washington Post" bold headlines, "An Act of Terror." Terror a word that means a lot especially in the prosecution going forward.

BERMAN: The "L.A. Times" says "Marathon blasts throw Boston into chaos." The "Houston Chronicle" talking about a father and a daughter who ran the race, it says, seconds may have saved the family.

CUOMO: So much of this about timing. Who made it and who got affected by the bombs? The telegraph in London says the clock showed 4:09:44. Then the shockwave hit. That period in a marathon when a large bulk of normal runners, you know, non-elite pro runners are coming through.

BERMAN: I'll tell you what the headlines in Boston would have been today. The headlines in Boston today would have been the winners of the Boston Marathon. That's not what we're seeing on the front pages today.

You know, there are a great many celebrities who call Boston home. And like anyone who has a tie to Boston right now, we're all reacting to yesterday's horrific events. This is what some of the celebrity Bostonians said last night.

(BEGIN VIDEO CLIP)

CONAN O'BRIEN, TV HOST: Boston is my hometown. It's where I grew up. It's where my family lives. So I wanted to take a moment to say that like everybody here, my thoughts and prayers are with the people of Boston, and everybody who's been affected by this absolutely senseless act.

TOM BERGERON, TV HOST: Now before we officially begin the show, we just want to take a moment. Our thoughts are with everyone in Boston tonight. I have family members and many friends there. My heart is with you.

(END VIDEO CLIP)

CUOMO: It's important to show how we come together because that's how you get through it. Ultimately you have to make a decision. Either you cave in to what happened or you decide to become stronger for it. And we're showing you these headlines. We're showing you these reactions.

We show the decision that was clearly made in Boston and around this country. Tweets from other famous Bostonians flooded in yesterday as well. Literally it was universal. Director Ben Affleck said such a senseless and tragic day. My family and I send our love to our beloved and resilient Boston.

BERMAN: Co-host of Extra, Maria Menounos who is from Medford said praying for everyone in Boston, devastated at the news. You know, the "New Kids on the Block," they're from Boston. Former New Kid Joey Macintyre, he was actually running in the marathon.

He tweeted this, moments after the bombs went off, there was an explosion by the finish line about 5 minutes after I finished. I'm OK, but I'm sure there are many hurt. Of course, there were, 144 injured and three people as we now know were killed.

CUOMO: And those are the people who become news celebrities in a way, the people whose lives were affected here, who have to fight through it, families who lost, families who've suffered. Those are the names that are going to matter the most.

We are going to take you through with team coverage, the fight for people's health, and their literally bodies that are going on in the hospitals right now also the investigation.

BERMAN: Ahead we're going to talk to Michael Sullivan, the former direct of the ATF and the U.S. attorney in Boston during September 11th. He joins us to walk through the latest on the investigation. And let me tell you, there's a lot going on right now this morning. Our live team coverage of the Boston bombings continues when we come back.

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CUOMO: Welcome back to this special edition of STARTING POINT. Our team coverage of this continuing situation in Boston, two bombs went off, marring a beautiful, cultural event, the Boston Marathon. Here with John Berman, I'm Chris Cuomo. We're looking at the headlines.

BERMAN: I want to show the headline right now. This is the front page of the "Boston Globe.' You can see it right here. It says marathon terror. And just the awful pictures of the blood on the sidewalks.

And again, what's so interesting about this is that the headline in the "Globe" today, every other day for 117 years no doubt would have been the winner of the Boston Marathon. Instead what we're seeing right now is the tragedy that unfolded on these streets right here behind us.

CUOMO: The challenge, of course, is or the injured to make it through their difficulties, for families to repair. For the investigation that is as wide-ranging as we've seen in one of these events. Find out who did this and why.

BERMAN: One of the youngest victims in this horrible attack has now been identified. The "Boston Globe" says it is a young man, Martin Richard, 8 years old from Dorchester, Massachusetts.

CUOMO: Picture just kills you because he's a beautiful little kid. This is first communion photo, his little white suit, the sign that was probably made by parents and god parents, a celebration of this kid's kind of entry into the world.

You know, him going to the sacrament as a Catholic. His father, to imagine the father's running the marathon. His wife is there. His daughter's there. His son is there. He has everything. And in a moment, in one way or another, it's lost.

Thank God his wife and his daughter still alive, but both hurt here. Just in a moment something that never needed to happen that has no sense to anybody changes the life --

BERMAN: He was there to hug his father, the kid was, and now this happened. We're on Commonwealth Avenue, about two blocks away from where this bombing happened. This is as close as we can get because the streets are shut down there as the investigation continues.

We are joined here by Michael Sullivan. He was the U.S. attorney in Boston during the attack on September 11th. He was also the acting director of the ATF. So good to have you here this morning, thanks for coming in.

MICHAEL SULLIVAN, BOSTON FORMER U.S. ATTORNEY/FORMER ATF ACTING DIRECTOR: Good to be with you guys this morning. Starting with these events, the picture and the story really tells the story. Everybody's thinking about the victims and the victims' families.

BERMAN: Meanwhile, while this happened, these two tracks, there were the victims, the recovery effort right there, there's also the investigation, and one of the things that people are looking into, these explosive devices, both the ones that went offer and apparently the ones that did not go off. What do you think they're looking at right now? SULLIVAN: Well, they're trying to capture all the forensic evidence that's going to be useful to them to determine how sophisticated the device was, whether or not they've seen similar devices in the past.

I mean, you know, the FBI and ATF have a wealth of expertise in this area. During the war in Iraq, they review every single improvised explosive device. We've been able to collect the evidence from the war zone and ship it back. It could be very helpful in terms of the forensics, analysis --

BERMAN: We have to tell you this is the type of thing we've seen all morning here. Convoys of National Guard -- these are police motorcycles and buses.

CUOMO: So there are so much personnel on the ground, so many different arms to the investigation that they are ferrying them around on buss and giving them police escorts to get to where they need to get. The bombs, when people are talking about them, what can it tell? The truth is everything. Every bomb tells a story.

SULLIVAN: Absolutely right. You know, some people look at it as rubble. The post blast investigation, they look at it as evidence. Two were detonated, two others that may have been a controlled blast by law enforcement all of that will be extremely helpful and useful.

BERMAN: what does the number of devices tell you? Two went off two others that didn't. Maybe more now, what does that tell you?

SULLIVAN: It tells how long the person has been planning the event in terms of the number of bombs they have. It might determine how sophisticated one is compared to the other, they will look at the component parts, see if they can trace where some of the parts come from.

It was designed obviously to do the maximum amount of harm. The way the first one got detonated and the second one just moments later, you know, to force people away from one explosion, potentially toward the next. That's a design by people who are terrorists. It's obvious too early to tell.

BERMAN: All right, Michael Sullivan, former U.S. attorney, acting head of the ATF, thank you so much for being with us.

SULLIVAN: Thank you so much.

BERMAN: He was here in his capacity, former law enforcement officer. Running for Senate right now here in Massachusetts, but all Senate campaigns have been suspended temporarily in the city while everyone comes together to recover from the awful event that happened in the city yesterday.

CUOMO: Shows what everyone puts first. Mr. Sullivan doesn't want to talk about the campaign. He wants to talk about his city healing. Hopefully in Washington politicians are dropping this as a political football and realize they have to be together to concentrate our energies and figuring who did this and why. At the same time, people who matter most are the victims and when we come back, we're going to go back to their stories. It is not over. The bombs have exploded, but people are fighting to keep their health and maybe their lives. We'll go to the situation and give you the latest information

(BEGIN VIDEO CLIP)

UNIDENTIFIED FEMALE: We were standing across from Lord & Taylor, and to the left of the finish line, two huge bombs, smoke coming out of buildings and something else to the left of that and the whole thing just went.

(END VIDEO CLIP)

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BERMAN: Welcome back, everyone. John Berman here along with Chris Cuomo, what we know now. We know more than 140 people hurt in this Boston marathon bombing. They have ended in the hospital. Many with the kind of injuries we have most seen in war zones -- Chris.

CUOMO: Absolutely. Sometimes people accuse the media of over dramatising a situation. We are not showing the photos of what we saw happened here yesterday. When we start treating those first responders as heroes, it's because they are. People were dismembered, almost bled out.

There are over 140 people who are injured. There are three people who lost their lives. Hopefully the number stays at three. It could have been much, much worse. Take our word for it. You cannot exaggerate the urgency that this being dealt with yesterday.

Senior medical correspondent Elizabeth Cohen joins us right now. You know, Elizabeth, you hear what we're talking about. Well, people are just injured. They must be OK. No, not at all, right? What is the severity? What is needed to make sure these people can leave the hospital.

ELIZABETH COHEN, CNN SENIOR MEDICAL CORRESPONDENT: Chris, the severity as you said. You can't say enough about how bad these injuries were and what heroes these first responders were. So in the hospital right now, about 144 people, 17 of them critically injured.

Amputations have been very, very common, more than 10 amputations. You can see that a lot of them are centered around Mass General, Beth Israel Hospital, Boston Medical, Tufts Medical Center, a part of Boston University.

And you I both spoke to two nurses on the scene at the time of all of this happened. And they told you, look, we've stabilized folks, got them to ambulances, but we know they have a long road ahead of them. Let's take a listen to what nurses said last night.

(BEGIN VIDEO CLIP) STEPHEN SEGATORE, FIRST RESPONDER: I treated both a double amputee. I treated a young child and also a young woman in a cardiac arrest. I think the -- the best scenario was that everyone turned from a, you know, this is a marathon, we're going to treat cramps, dehydration.

From that to all of a sudden everyone who had trauma experience came to the front and came back and led us to your -- you know, to experience and we did trauma care and did everyone we could to the medical centers.

(END VIDEO CLIP)

COHEN: Stephen Segatore, the nurse we just heard from said that his toughest moment, when he was treating a young woman maybe in her early 20s, blond hair, blue eyes, he thought he could save her, but her abdomen was open, her leg was broken. She wasn't breathing. He gave her CPR. He tried. He wasn't able to save her and she died in front of him -- Chris, John.

CUOMO: A horrible story, but again, perspective. Elizabeth, thank you. We'll come back to you, obviously, perspective on this, John, this is a horrible story to hear and see the face of that beautiful little boy that was lost. When are you dealing with injuries like this, when we saw the photos of what was going on there yesterday, amazing that people are alive today.

BERMAN: And they were able to save so many and so many people getting the best treatment in the world.

CUOMO: Absolutely. Look, we're doing team coverage on this because there are so many moving parts. John and I are on the ground here in Boston. Others are here. We'll take you through the latest in the investigation. All resources on the ground right now, they are doing searches, they are getting leads. We will tell you the latest we know on who may have done this and why.